1. Field of the Description
This invention generally relates to semiconductor processing, and, more particularly, to the isolation of transistors formed on a substrate.
2. Description of the Related Art
The implementation of electrical circuits requires connecting isolated devices through very specific electrical paths. As it relates to the fabrication of various integrated circuits on, for example, a silicon substrate, this means that the various devices formed in the silicon must be electrically isolated from one another. Such devices, when properly isolated, may thereafter be interconnected to create specific electrical circuits.
The ability to effectively isolate electrical devices, such as transistors, from one another is very important in the fabrication of integrated circuits. For example, effective isolation of electrical field effect transistors is highly desirable to prevent the establishment of unwanted parasitic channels between adjacent devices. Yet another example is the requirement for effective isolation of the collector regions of bipolar integrated circuits.
Generally speaking, the deeper an isolation structure extends into the surface of the substrate, the better the performance of the isolation structure. However, problems have been encountered as the depth of single width trenches has been increased. For example, with deep, single width trenches, problems have arisen at the intersection of the trench with the surface of the substrate. The problems have included, but are not limited to, lack of adhesion of process layers on the surface of the substrate, cracks in the substrate and/or the process layers, and delamination of process layers, etc.
The present invention is directed to a method and device that solves some or all of the aforementioned problems.